Prior art knows different methods for authenticating users of data transfer devices. One authentication method is based on the use of a SIM card (Subscriber Identity Module) placed in the data transfer device, the method requiring, however, a smart card reader in the data transfer device. Moreover, the solution is not easy to apply in situations where a data transfer service is to be used temporarily, maybe only once, on the data transfer service, because for that purpose a SIM card would have to be delivered to the data transfer device of the user.
U.S. Pat. No. 6,112,078, which is incorporated herein as a reference, discloses a solution which does not include a SIM card and in which at least some of the authentication data are transmitted to a mobile station or a paging device which the user of the data transfer device has at his/her disposal. For reasons of data security, all the authentication data, for example the user ID and the password, are not sent over the same the transmission path.